Publications

Directions of natural remanent magnetization are used to identify and correlate individual cooling units in the middle Tertiary ash-flow province in central and eastern Nevada and western Utah. Potassium-argon dating indicates that the minimum time between eruptions of individual but genetically related ash-flow cooling units is on the order of 0.8 m.y. As this interval is long in comparison with

Paleomagnetic data and potassium-argon ages indicate that the Sonoma Volcanics was erupted during the Pliocene Gilbert reversed and Gauss normal polarity epochs. The Gilbert reversed epoch is represented in the Howell Mountains east of Napa and east of St. Helena, in the mountains immediately east of the Valley of the Moon, and on the hill just north of Santa Rosa. The Gauss normal epoch is repres

Observed gravity values, station locations, terrain corrections, and Bouguer gravity data are provided in tabular form for approximately 450 gravity observations in southwestern Utah.

This collection of 37 short papers is the second published chapter of "Geological Survey Research 1972." The papers report on scientific and economic results of current work by members of the Conservation, Geologic, and Water Resources Divisions of the U.S. Geological Survey.Chapter A, to be published later in the year, will present a summary of significant results of work done ~n fiscal year 1972

No abstract available.

Two main types of deformational breccia occur in the Sierra Madera cryptoexplosion structure: monolithologic breccias composed of shattered rock of a single lithology and mixed breccias composed of rocks of several lithologies. Monolithologic breccias generally show no mineralogic signs of shock deformation, but a few samples are shatter-coned in a manner suggesting simultaneous formation of brecc

Recognition of a nonmarine to marine transition in sedimentary rocks at Glade Creek and Big Bar in the southern Klamath Mountains permits reconstruction of the approximate position of a north-trending Early Cretaceous (Valanginian) shoreline. At the southern end of the Klamath Mountains, the shoreline is displaced 60 mi or more to the east by a west-northwest-trending fault zone. South of this fau

No abstract available.

New evidence indicates that high-grade regionally metamorphosed marble and quartzite in the northern Ruby Mountains are Paleozoic strata. Correlation is based on a match of the lithologic sequence to strata of Cambrian to Devonian age in nearby areas; particularly diagnostic is a brown dolomite at the base of the Cambrian carbonate sequence. The metamorphic complex contrasts with unmetamorphosed

Several thousand small earthquakes, with magnitudes ranging up to 4, occurred near Danville, California, during May, June, and July 1970. Seven temporary seismographs were installed near the epicentral region to augment an existing telemetered network within 1 day after the first felt earthquake. The dense concentration of 10 seismographs within 12 km of the seismic activity and the existence of a

The Yukon-Koyukuk province covers 100,000 sq mi (259,000 sq km) along the west coast of Alaska, extending from the Brooks Range to the Yukon delta, but excluding the Seward Peninsula. It is essentially a vast tract of Cretaceous rocks locally veneered by Quaternary alluviated beds and volcanic rocks. The Cretaceous section contains a large volume of volcanic rocks, and most of the sedimentary sequ

No abstract available.